Changes in the incidence and overall survival of patients with myeloproliferative neoplasms between 2002 and 2016 in the United States

Abstract

This analysis examined trends in incidence and survival among US adults with myeloproliferative neoplasms, including essential thrombocythemia (ET; n = 14,676), polycythemia vera (PV; n = 15,141), and primary myelofibrosis (PMF; n = 4214), using Surveillance, Epidemiology, and End User Results (SEER) data (SEER 18; 2002–2016). Incidence and survival rates over the study period and by diagnosis year (per 5-year time frames: 2002–2006; 2007–2011; 2012–2016) were assessed. The overall incidence rates (95% CI) were 1.55 (1.52–1.57) for ET, 1.57 (1.55–1.60) for PV, and 0.44 (0.43–0.45) per 100,000 person-years for PMF, with rising ET incidence. Five-year mortality over the study period was 19.2%, 19.0%, and 51.0% for ET, PV, and PMF, respectively. Improved survival over time was observed for PV and PMF, but not for ET. These findings highlight the need for effective ET therapies, as ET incidence has risen without concurrent improvements in survival over the past 2 decades.

Keywords:

• Essential thrombocythemia
• incidence
• myeloproliferative neoplasms
• polycythemia vera
• primary myelofibrosis
• survival

Introduction

The Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), including essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (PMF), are a group of heterogeneous clonal hematopoietic cell disorders driven by recurrent somatic mutations [1,2]. MPNs are associated with an increased risk for thrombotic events and leukemic transformation [3–5]. Furthermore, patients with MPNs have reduced overall survival compared with the general population [6,7] and are burdened by a variety of constitutional symptoms such as fatigue, night sweats, pruritus, and bone pain [8,9].

The incidence of MPNs varies by several factors, including subtype and geographic region [2,10,11]. In the United States, previous reports based on registry data have shown incidence rates of 0.7 to 1.0 per 100,000 person-years for ET, 0.9 to 1.1 for PV, and 0.3 to 1.0 for PMF [12–14], with evidence of increasing incidence over time [13]. Currently available survival data for patients with MPNs are also generally based on retrospective analyses of patients from large medical centers. These studies report that patients with PMF have the shortest survival time, with median overall survival of 19.8 years among patients with ET, 13.5 years for PV, and 5.2 to 5.9 years for PMF [5,15,16]. Recent studies suggest survival has generally improved among patients with myelofibrosis over the past decade [17,18], but similar studies for ET and PV are lacking.

There are several challenges to maintaining accurate, population-based, epidemiological reporting of MPNs, including evolving disease classifications, changes in diagnostic procedures, and potential under-reporting of MPNs to cancer registries [12,19]. Contemporary analyses of MPN incidence and survival using updated registry data are needed, as most of the recent real-world analyses of US patients were conducted on periods up to 2012. Furthermore, data on how MPN epidemiology has changed over time are lacking. The objective of this analysis was to describe trends in MPN incidence and overall survival over time in the United States using data through 2016 from the Surveillance, Epidemiology, and End Results (SEER) database.

Design and methods

Data source

All data were extracted from the SEER 18 registry (2002–2016). Sponsored by the National Cancer Institute, the SEER program publishes cancer incidence and survival data from population-based cancer registries covering approximately 35% of the US population [20]. Ethical approval was obtained from institutions participating in SEER registry data deposition through their respective institutional review boards; the SEER program receives only de-identified patient data. The current analysis was exempt from ethical review as no personally identifying information was collected or reported.

Study cohort

Adult patients with evidence of ET, PV, or PMF were identified from the SEER 18 registry using the primary site of bone marrow (C421) and International Classification of Diseases for Oncology (ICD-O) histology codes (ICD-O-3: 9962 for ET, 9950 for PV, and 9961 for PMF). The date of the first diagnosis served as the index date. Patients aged <18 years on the index date, those who were missing demographic or survival information, and patients with multiple MPN diagnoses (i.e. those with index ET with a subsequent PV diagnosis, index PV with a subsequent ET diagnosis, or index PMF with a subsequent diagnosis of ET/PV) were excluded from the analysis.

Data collection

Demographic and clinical characteristic data for patients included in the analysis were collected retrospectively. Age-adjusted incidence rates (per 100,000 person-years) for each MPN subtype were determined for patients with diagnosis dates during the entire period from 2002 to 2016, as well as for three 5-year diagnosis periods (2002–2006, 2007–2011, and 2012–2016), and each 1-year diagnosis period from 2002 to 2016. Mortality rates for all MPN subtypes combined and for each individual subtype were analyzed over the full study period and for each of the 5-year diagnosis periods. Median overall survival for each MPN subtype was also assessed.

Statistical analyses

Age-adjusted incidence rates (per 100,000 person-years) were standardized to the US population in the year 2000. The Tiwari method was used to calculate confidence intervals for rates and rate ratios [21]. One-, 2-, and 5-year mortality rates by diagnosis year, categorized into 3 groups (2002–2006, 2007–2011, and 2012–2016), were compared using Kaplan–Meier methodology; patients were censored at the end of each 5-year diagnosis period.

Results

Patients

In total, 34,031 patients (ET, n = 14,676; PV, n = 15,141; PMF, n = 4214) were included in the study. Median age was similar across cohorts (ET, 67.0 y; PV, 65.0 y; PMF, 70.0 y), and 50.5% of patients overall were female (ET, 61.2%; PV, 42.9%; PMF, 40.4%; Table 1). The time period with the highest proportion of diagnosed patients (38.9%) was 2012 to 2016 (ET, 41.0%; PV, 36.3%; PMF, 40.4%).

Table 1. Demographics and baseline clinical characteristics of the study population (SEER 18; 2002–2016).

Variable	ET (n = 14,676)	PV (n = 15,141)	PMF (n = 4214)
Age, median (IQR), y	67.0 (54–78)	65.0 (54–76)	70.0 (61–78)
<60 y, n (%)	4967 (33.8)	5586 (36.9)	–
≥60 y, n (%)	9709 (66.2)	9555 (63.1)	–
<65 y, n (%)	–	–	1448 (34.4)
≥65 y, n (%)	–	–	2766 (65.6)
Sex, n (%)
Female	8982 (61.2)	6492 (42.9)	1702 (40.4)
Male	5694 (38.8)	8649 (57.1)	2512 (59.6)
Race, n (%)
White	11,465 (78.1)	12,867 (85.0)	3478 (82.5)
Black	1727 (11.8)	1037 (6.9)	344 (8.2)
Asian/Pacific Islander	1075 (7.3)	923 (6.1)	308 (7.3)
American Indian/Alaska native	77 (0.5)	71 (0.5)	20 (0.5)
Unknown	332 (2.3)	243 (1.6)	64 (1.5)
Year of diagnosis, n (%)
2002–2006	3564 (24.3)	4793 (31.7)	1099 (26.1)
2007–2011	5090 (34.7)	4847 (32.0)	1413 (33.5)
2012–2016	6022 (41.0)	5501 (36.3)	1702 (40.4)

Abbreviations: ET: essential thrombocythemia; IQR: interquartile range; PMF: primary myelofibrosis; PV: polycythemia vera; SEER: Surveillance, Epidemiology, and End Results.

MPN incidence

Over the entire study period, incidence rates (95% CI) for ET, PV, and PMF were 1.55 (1.52–1.57), 1.57 (1.55–1.60), and 0.44 (0.43–0.45) per 100,000 person-years, respectively (Table 2). Significantly higher annual incidence rates were observed among older patients (≥60 y for ET/PV or ≥65 y for PMF) compared with younger patients (<60 y for ET/PV or <65 y for PMF) for all MPN subtypes (ET, 4.65 [4.56–4.75] vs 0.66 [0.64–0.67]; PV, 4.54 [4.45–4.64] vs 0.72 [0.70–0.74]; PMF, 1.80 [1.73–1.87] vs 0.16 [0.15–0.17]). The annual incidence rates of PV and PMF were higher for male versus female patients (1.94 [1.90–1.98] vs 1.23 [1.20–1.26] and 0.59 [0.57–0.62] vs 0.33 [0.31–0.34], respectively); however, the ET incidence rate was higher for female patients (1.73 [1.70–1.77] vs 1.34 [1.31–1.38]). Across MPN subtypes, incidence rates did not significantly differ based on race; however, the highest incidence of ET was observed among Black patients (1.81 [1.72–1.90]), whereas PV and PMF rates were highest among White patients (1.67 [1.64–1.70] and 0.45 [0.44–0.47], respectively; Table 2). Evaluation of changes in incidence over time demonstrated a nonsignificant increase in ET incidence across the three diagnosis periods (2002–2006, 1.24 [1.20–1.29]; 2007–2011, 1.62 [1.58–1.67]; 2012–2016, 1.73 [1.69–1.78]), whereas PV and PMF remained relatively stable. Likewise, analysis of annual age-adjusted incidence rates over the entire study period showed that the incidence of ET, but not PV or PMF, rose steadily from 2002 to 2016 (Figure 1(A)). When compared against prior SEER analyses for reference [12,13,22], the annual age-adjusted incidence rates in the current analysis were higher across all MPN subtypes (Figure 1(B)).

Figure 1. Annual age-adjusted MPN incidence in the United States. (A) Annual incidence over time in the current analysis and (B) age-adjusted MPN incidence rates per current and past SEER analyses. ET: essential thrombocythemia; MPN: myeloproliferative neoplasm; PMF: primary myelofibrosis; PV: polycythemia vera; SEER: Surveillance, Epidemiology, and End Results. The current analysis used the SEER 18 registry. Age-adjusted incidence rates (per 100,000 person-years) were standardized to the 2000 US population.

Table 2. Annual MPN incidence in the United States between 2002 and 2016^a.

	ET (n = 14,676)		PV (n = 15,141)		PMF (n = 4214)
Variable	Cases	Rate^b (95% CI)	Cases	Rate^b (95% CI)	Cases	Rate^b (95% CI)
Total^c	14,793	1.55 (1.52–1.57)	15,261	1.57 (1.55–1.60)	4227	0.44 (0.43–0.45)
Age
<60 y	4967	0.66 (0.64–0.67)	5586	0.72 (0.70–0.74)	–	–
≥60 y	9709	4.65 (4.56–4.75)	9555	4.54 (4.45–4.64)	–	–
<65 y	–	–	–	–	1448	0.16 (0.15–0.17)
≥65 y	–	–	–	–	2766	1.80 (1.73–1.87)
Sex
Female	8982	1.73 (1.70–1.77)	6492	1.23 (1.20–1.26)	1702	0.33 (0.31–0.34)
Male	5694	1.34 (1.31–1.38)	8649	1.94 (1.90–1.98)	2512	0.59 (0.57–0.62)
Race
White	11,465	1.51 (1.48–1.54)	12,867	1.67 (1.64–1.70)	3478	0.45 (0.44–0.47)
Black	1727	1.81 (1.72–1.90)	1037	1.08 (1.01–1.15)	344	0.37 (0.33–0.41)
American Indian/Alaska native	77	0.84 (0.65–1.06)	71	0.65 (0.50–0.84)	20	0.21 (0.12–0.34)
Asian/Pacific Islander	1075	1.21 (1.14–1.29)	923	1.03 (0.96–1.10)	308	0.34 (0.30–0.38)
Unknown	332	NA	243	NA	64	NA
Year of diagnosis
2002–2006	3564	1.24 (1.20–1.29)	4793	1.65 (1.61–1.70)	1099	0.38 (0.36–0.41)
2007–2011	5090	1.62 (1.58–1.67)	4847	1.52 (1.48–1.56)	1413	0.45 (0.42–0.47)
2012–2016	6022	1.73 (1.69–1.78)	5501	1.55 (1.51–1.59)	1702	0.48 (0.46–0.50)

Abbreviations: ET: essential thrombocythemia; MPN: myeloproliferative neoplasm; NA: not available; PMF: primary myelofibrosis; PV: polycythemia vera; SEER: Surveillance, Epidemiology, and End Results.

^aUsing the SEER 18 registry. Howlader N, Noone AM, Krapcho M, et al. SEER Cancer Statistics Review, 1975–2017, National Cancer Institute. Bethesda, MD. Available at: https://seer.cancer.gov/csr/1975_2017/. Accessed 8 January 2021.

^bRate per 100,000 person-years.

^cTotal incidence was calculated in the population prior to exclusions (i.e. index myelofibrosis with subsequent ET/PV diagnosis or index ET/PV with subsequent PV/ET diagnosis) for additional analyses.

MPN mortality

For the Kaplan–Meier mortality analysis, the median (interquartile range) follow-up times were 4.1 (1.8–7.8) years for ET, 4.7 (2.1–8.3) years for PV, and 2.4 (0.9–4.7) years for PMF. Five-year mortality over the full study period was 19.2%, 19.0%, and 51.0% for ET, PV, and PMF, respectively. Mortality rates slightly decreased for PV and PMF, but not for ET, over the 3 time periods (Figure 2). Over the course of the study, the 5-year mortality rate decreased from 12.2% (2002–2006) to 11.1% (2012–2016) among patients with PV and from 38.3% (2002–2006) to 36.1% (2012–2016) among those with PMF; 5-year mortality among patients with ET increased from 10.6% (2002–2006) to 12.0% (2012–2016). The 5-year mortality rate for the entire study population (i.e. all MPNs combined) was 14.6% during 2002 to 2006, 15.8% from 2007 to 2011, 14.6% from 2012 to 2016, and 23.0% for the full study period. The median (95% CI) overall survival for the entire period was 12.0 (11.7–12.3) years for patients with ET, 12.0 (11.7–12.4) years for those with PV, and 3.6 (3.4–3.8) years for patients with PMF (Figure 3). Median survival was not reached in each of the three diagnosis periods (2002–2006, 2007–2011, 2012–2016) for ET or PV; Kaplan–Meier survival curves showed that ET survival remained unchanged (Figure 4(A)), whereas PV survival improved during the most recent period (2012–2016; Figure 4(B)). Improved overall survival was also observed in patients with PMF over time (median [95% CI]: 2002–2006, 3.3 [2.4–3.6] y; 2007–2011, 3.6 [3.3–4.3] y; 2012–2016, 3.8 [3.5–4.2] y; Figure 4(C)). Median survival was lower for older patients (≥60 y for ET/PV or ≥65 y for PMF) compared with younger patients (<60 y for ET/PV or <65 y for PMF) across all MPN subtypes (ET, 8.1 y vs not reached, respectively; PV, 8.2 y vs not reached; PMF, 2.7 vs 7.8 y).

Figure 2. Kaplan–Meier estimation of mortality rates for MPNs in the United States. 1-, 2-, and 5-year mortality rates for (A) ET, (B) PV, and (C) PMF over 3 time periods. ET: essential thrombocythemia; MPN: myeloproliferative neoplasm; PMF: primary myelofibrosis; PV: polycythemia vera; SEER: Surveillance, Epidemiology, and End Results. The analysis used the SEER 18 registry. Patients with missing values for survival were excluded from the mortality analysis (ET, n = 37; PV, n = 198; PMF, n = 5). Patients were censored at the end of each 5-year analysis time frame (i.e. 2002–2006, 2007–2011, 2012–2016).

Figure 3. Overall survival for (A) ET, (B) PV, and (C) PMF in the United States between 2002 and 2016. ET: essential thrombocythemia; MPN: myeloproliferative neoplasm; PMF: primary myelofibrosis; PV: polycythemia vera; SEER: Surveillance, Epidemiology, and End Results. The analysis used the SEER 18 registry. Patients with missing values for survival were excluded from the mortality analysis (ET, n = 37; PV, n = 198; PMF, n = 5).

Figure 4. Overall survival for (A) ET, (B) PV, and (C) PMF in the United States by diagnosis period (2002–2006; 2007–2011; 2012–2016). ET: essential thrombocythemia; MPN: myeloproliferative neoplasm; PMF: primary myelofibrosis; PV: polycythemia vera; SEER: Surveillance, Epidemiology, and End Results. The analysis used the SEER 18 registry. Cohort sizes were as follows: (A) 2002–2006, n = 3555; 2007–2011, n = 5076; 2012–2016, n = 6008; (B) 2002–2006, n = 4725; 2007–2011, n = 4780; 2012–2016, n = 5438; (C) 2002–2006, n = 1097; 2007–2011, n = 1410; 2012–2016, n = 1702.

Discussion

Large-scale, contemporary epidemiological studies are needed to better understand how MPN epidemiology is evolving as disease classification and diagnostics continue to change. This study presents a population-based analysis of MPN incidence and survival in the United States based on the most recent data from the SEER registry, which collects information from several cancer registries covering approximately 35% of the US population [23]. The incidence over the entire study period (2002–2016) was found to be 1.55, 1.57, and 0.44 per 100,000 person-years for ET, PV, and PMF, respectively. The incidence rose over time for ET, whereas the incidence of PV and PMF remained relatively stable over the three time periods examined. Incidence rates were significantly higher among older patients for all MPN subtypes. Sex-specific differences were also observed, with higher incidence rates of PV and PMF among male patients while ET incidence was significantly higher in female patients. Five-year mortality rates over the full study period were 19.2% among patients with ET, 19.0% for PV, and 51.0% for PMF. Median overall survival for patients with PMF was particularly poor (3.6 vs 12.0 y for both ET and PV).

MPN incidence rates in the current study were higher than those reported in previous SEER analyses conducted through 2012, which estimated incidence rates of 0.7 to 1.0 per 100,000 person-years for ET, 0.9 to 1.1 for PV, and 0.3 for PMF [12,13]. Additionally, a recent review of MPN incidence in the United States from 2001 to 2016 by Shallis et al. cited overall incidence rates of 1.1, 1.2, and 0.33 per 100,000 person-years for ET, PV, and PMF, respectively [22]. Possible confounders in incidence determination include increased or earlier use of genetic testing to facilitate an MPN diagnosis after 2012 and reporting delays, as SEER allows cases reported for a given year during the initial analysis to be added to the registry in subsequent data submissions. In fact, a prior SEER study noted delayed reporting rates of up to 49% for ET and 36% for PV, leading to substantially higher incidence rates reported for previous years in later data files [12]. It is unclear why incidence in this study was higher than SEER data reported in the 2020 review by Shallis et al. over essentially the same time frame (2001–2016) [22]; methodology for incidence rate standardization and for identifying patients with MPNs was not reported in that study, so we are unable to speculate on differences in patient populations between the two studies. Interestingly, the incidence of PV remained stable over the three time periods assessed, even after the 2008 World Health Organization (WHO) reclassification to include JAK2 V617F mutation as a major criterion for PV diagnosis [24]. Overall, incidence rates fell within the ranges reported in several other countries, including France (1980–2004; ET, 1.2; PV, 0.6; PMF, 0.4 per 100,000 person-years), Sweden (2000–2014; ET, 1.6; PV, 1.5; PMF, 0.5 per 100,000 person-years), Australia (2003–2014; ET, 1.0; PV, 0.9; PMF, 0.5 per 100,000 person-years), Korea (2004–2013; ET, 2.4; PV, 1.2; PMF, 0.4 per 100,000 person-years), and Canada (2011–2015; ET, 1.2; PV, 0.4; PMF, 0.8 per 100,000 person-years) [25–29]. Additionally, a meta-analysis of 34 studies containing MPN incidence data from populations in Europe, North America, and Australasia found pooled crude incidence rates of 1.0 per 100,000 person-years for ET, 0.8 for PV, and 0.5 for PMF; however, age-adjusted rates were not reported in the study [11]. The sex-specific (i.e. higher rates of PV and PMF among males and ET among females) and age-related (i.e. higher incidence of all MPNs among older populations) effects identified in this analysis were also observed in many of these previous studies [26–29]. Taken together, these findings suggest that although some variation in MPN incidence exists across geographic regions, trends in which patient populations are most affected were generally preserved.

In accordance with prior analyses from the United States and Europe, patients with PMF had the worst survival outcomes; however, the median overall survival of patients with MPNs observed in this study was worse than has been previously reported, with prior estimates of median overall survival for patients with ET, PV, and PMF of 19.8, 13.5, and 5.2 to 5.9 years, respectively [5,15,16]. Factors contributing to this discrepancy could include differences in sources of study populations, disease diagnostic criteria, patient demographics, disease characteristics, and disease management. The SEER database includes patients from a variety of practice types (e.g. community, academic), whereas previous single- or multi-center studies typically included patients managed at large academic centers or centers of excellence. As SEER does not report specific details on how diagnoses were made, it is not possible to determine the proportion of patients who met strict WHO diagnostic criteria [30] and how many patients were diagnosed based on less stringent criteria or physician judgment alone. Differentiation of ET from prefibrotic MF can be particularly challenging [30], and some patients in the registry may have been misdiagnosed. Misdiagnosis of prefibrotic PMF as ET could be one contributing factor to the shorter ET survival than has been previously observed in some studies (e.g. up to 30 years in a study of patients diagnosed with ET per 2016 WHO criteria from Italian tertiary centers) [31]. Notably, the prognosis for patients with prefibrotic PMF is far better than that of overt PMF, with prior real-world studies estimating median overall survival of approximately 15 to 17 years specifically in prefibrotic PMF [31,32]. In addition to variations in diagnostic criteria, patients in the current study were older than those in the prior analyses. A trend toward improved survival over time was observed among patients with PV and PMF, but not for those with ET. This finding may reflect the lack of effective treatment options available for ET. The Janus kinase (JAK) 1/JAK2 inhibitor ruxolitinib is approved by the US Food and Drug Administration (FDA) for the treatment of PV in adults who have an inadequate response to or are intolerant of hydroxyurea [33] and significantly improved the clinical course of PV versus standard therapy in a phase 3 trial [34]. Both ruxolitinib and the JAK2 inhibitor fedratinib have been shown to improve splenomegaly and myelofibrosis symptoms in phase 3 studies [35–37] and are approved by the FDA for use in patients with intermediate- or high-risk myelofibrosis [33,38]. Furthermore, ruxolitinib treatment conferred a survival benefit in the phase 3 COMFORT trials [36,39]. Increasing the use of these agents in community practice may contribute to survival benefits observed in PV and PMF. Accordingly, an analysis of Medicare claims demonstrated significantly improved overall survival among patients with PMF in the period following ruxolitinib approval (2012–2017) versus pre-approval (2010–2011), with additional survival benefit observed among those who received ruxolitinib (1-y survival: pre-ruxolitinib approval, 55.6%; post-ruxolitinib approval/ruxolitinib-unexposed, 72.5%; post-ruxolitinib approval/ruxolitinib-exposed, 82.3%) [17]. Additionally, a single institution chart audit study showed that patients with myelofibrosis diagnosed after 2010 had improved survival compared with those diagnosed prior to 2010 (median survival, 66 vs 48 months, respectively), regardless of age or risk status, and also showed additional improvements for patients who received ruxolitinib (median survival, 98 vs 91 months for no ruxolitinib) [18]. In contrast, two recent studies reported no improvement in survival among patients with myelofibrosis during the ruxolitinib era. First, a retrospective study from the SEER-Medicare database showed that survival did not improve in a later (2012–2015) versus earlier (2007–2011) diagnosis period for older patients (>65 y) with myelofibrosis (median survival, 2.62 vs 2.70 y, respectively), regardless of ruxolitinib status (median survival, 2.76 y for ruxolitinib-treated vs 2.53 y for non–ruxolitinib-treated) [40]. Second, a SEER analysis showed no improvement in 4-year relative survival rates for PMF in the years following ruxolitinib approval (2012–2016) versus pre-approval (2007–2011; 56% vs 55%, respectively) [41]. It should be noted that disease risk status and myelofibrosis type (i.e. primary vs secondary) were not provided in the first study, and disease risk status and ruxolitinib use were not described in the latter study. Additionally, the cohort of ruxolitinib-treated patients was small (n = 113) and duration of use was short (median, 11.9 months) in the first study of elderly patients, and time points selected for analysis differed across studies. Poor uptake of ruxolitinib use in clinical practice and sub-optimal dosing strategies may have contributed to the lack of survival benefit observed in these studies.

Limitations of the current study include those inherent to retrospective registry analyses, such as the potential for misdiagnosis and incomplete or inaccurate medical records. SEER does not differentiate between prefibrotic and overt PMF, nor does it provide details on some important clinical characteristics such as the degree of bone marrow fibrosis. Additionally, data on mutation status and factors driving changes in MPN incidence and survival (e.g. treatment patterns, diagnostic criteria, comorbidities) were not available for analysis.

Conclusions

In this nationally representative real-world study of patients with MPNs in the United States, the incidence of ET appeared to increase over time from 2002 to 2016. The median overall survival of patients with ET, PV, and PMF was shorter than has been reported in previous studies. A trend toward improved survival over time was observed among patients with PV and PMF but was not apparent in patients with ET. Further investigation into the varying survival rates among MPN subtypes is warranted, as findings from this study may suggest improvements in supportive care strategies or therapies for ET are lagging behind those available in PV and PMF.

Acknowledgments

Writing assistance was provided by Jane Kovalevich, PhD, an employee of ICON (North Wales, PA, USA), and was funded by Incyte Corporation (Wilmington, DE, USA).

Disclosure statement

SVerstovsek received research support from AstraZeneca, Blueprint Medicines Corp., Celgene, CTI BioPharma Corp., Genentech, Gilead, Incyte Corporation, ItalPharma, Novartis, NS Pharma, PharmaEssentia, Promedior, Protagonist Therapeutics, Roche, and Sierra Oncology, and is a paid consultant for Celgene, Incyte Corporation, Novartis, and Sierra Oncology. JY, RMS, and SP are employees and shareholders of Incyte Corporation. SVerma and CD are employees of STATinMED Research, which is a paid consultant of Incyte Corporation. C-CC was an employee of STATinMED Research, which is a paid consultant of Incyte Corporation, at the time of the analysis.

Data availability statement

Access to individual patient-level data is not available for this study. Information on Incyte’s clinical trial data sharing policy and instructions for submitting clinical trial data requests are available at: https://www.incyte.com/Portals/0/Assets/Compliance%20and%20Transparency/clinical-trial-data-sharing.pdf?ver=2020-05-21-132838-960

Additional information

Funding

This work was supported by Incyte Corporation (Wilmington, DE, USA).